In certain audio communications systems it is desirable to have full room audio (acoustic) pickup. One solution to realize full room coverage is to use a single omni-directional microphone. Use of such an omni-directional microphone, however, has several limitations, namely, the pickup of sound echoes or reverberation as well as noise from the room. Moreover, in two-way communications systems using, for example, a speakerphone, the acoustic coupling between the receiving loudspeaker and microphone leads to objectionable echoes and/or annoying switching transients because of the required use of switched loss in the speakerphone.
The limitations of the omni-directional microphone lead to the consideration of using directional microphones in such communications system. Directional gradient type microphone elements using internal acoustic subtraction are commercially available. However, use of the directional gradient type microphone in an apparatus requires a prior knowledge of the location of a talker relative to the apparatus. Consequently, to obtain full room coverage, a plurality of such directional gradient type microphones would be required. This solution, however, is complex and expensive.